Polyimides are known in the art for use in the manufacture of integrated circuits including chips (e.g., chip back end of line, or "BEOL"), thin film packages, and printed circuit boards. Polyimides are useful in forming dielectric interlayers, passivation layers, alpha particle barriers, and stress buffers. Polyimides are particularly useful as an interlayer dielectric material to insulate the conductor wiring interconnecting the chips on a multichip module. This is known as "thin film" wiring. Multichip modules represent an intermediate level of packaging between the chips and the circuit board, and are generally known in the art. Multichip modules are made up of multiple layers of power, signal, and ground planes which deliver power to the chips and distribute the input/output signals between chips on the module or to and from the circuit board.
There is a continuing desire in the microelectronics industry to increase the circuit density in multilevel integrated circuit devices, e.g., memory and logic chips, thereby increasing performance and reducing cost. In order to accomplish these goals, those in the field are striving to reduce the minimum feature sizes, e.g.,metal lines and vias, and to decrease the dielectric constant of the interposed dielectric material to enable closer spacing of circuit lines without a concomitant increase in crosstalk and capacitive coupling. Polyimides usually have dielectric constants of about 3.0-3.8 and mechanical and thermal properties sufficient to withstand present processing operations including the thermal cycling associated with semiconductor manufacturing. However, there is a need in the art for a dielectric material that would be suitable for use in integrated circuit devices, wherein the material exhibits a lower dielectric constant (e.g., &lt;3.0) than typically exhibited by polyimides and has improved mechanical and thermal properties.
The invention is addressed to the aforementioned need in the art, and, in one embodiment, provides a novel dielectric composition that represents a significant improvement over prior dielectric materials used in integrated circuit devices. The composition is formed by imidizing and curing an oligomeric precursor compound comprised of a central polyamic acid or polyamic acid ester segment terminated at each end with an aromatic species substituted with two or more aryl-substituted ethynyl moieties. These oligomeric compounds, dielectric compositions formed therefrom, and associated methods of manufacture and use will be discussed in detail herein.
Compounds that are end-capped with two or more diaryl-substituted acetylene moieties at each of two termini are known and described, for example, in PCT Publication No. WO 97/10193. The reference does not, however, describe end-capped oligomeric segments comprised of polyamic acid, a polyamic acid ester, or the like.
U.S. Pat. No. 5,138,028 to Paul et al. is also of interest insofar as polyimides end-capped with diaryl-substituted acetylene are disclosed. Only one diaryl-substituted acetylene moiety is present at each terminus, resulting in higher curing temperature and less efficient cross linking than possible with the oligomeric precursor compounds of the invention.
John et al. (1994), "Synthesis of Polyphenylenes and Polynaphthalenes by Thermolysis of Enediynes and Dialkynylbenzenes," J. Am. Chem. Soc. 116:5011-5012, is of background interest insofar as the publication describes thermal polymerization of substituted enediynes. U.S. Pat. No. 5,773,197 to Carter et al. is also a background reference that is of interest with respect to the present invention, in that the patent describes the manufacture and use of integrated circuit devices in which a dielectric material contained therein is synthesized on a substrate.
No art of which applicants are aware, however, describes or suggests the dielectric compositions as now provided herein, or the oligomeric precursor compounds that are imidized and crosslinked to form the compositions. In contrast to the dielectric materials of the prior art, the present compositions provide the following advantages: (1) the precursor to the present dielectric compositions has a lower solution viscosity than other polyimide precursors, allowing for superior planarization and gap filling; (2) the present dielectric compositions have a low dielectric constant, less than 3.0, which is lower than that of currently used dielectric materials; and (3) films of the novel dielectric compositions have superior mechanical properties relative to current dielectric materials used in the manufacture of integrated circuit devices and packages. The compositions also find utility in laminates, composites and the like.